When embedding, the fonts are gathered and added to the ODF
document. This change in addition adds the functionallity to
embed used fonts only and filtering out of font scripts. When
embedding used fonts only, they are filtered depending on if
the style (referencing the font) is in use and in addition if
the font is used in direct formatting.

Change-Id: I1ba0066b1eb34bdde7247eeb63c1be5a91db984d
Reviewed-on: https://gerrit.libreoffice.org/57168
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>